Ultrafiltration of the Parathyroid Hormone

I. T. OLIVER AND W. A. RAWLINSON I955 the effect of the free aldehyde group. The Soret band of the oxime of the copper complex, in addition to being shifted to shorter wavelengths, is much more intense than that of the copperporphyrin a itself. The similarity of the absorption spectra of copper-porphyrin a and pyridine-haemochrome a, and their difference from the usual two-banded systems of most covalent metal-porphyrin derivatives, leads us to consider cytochrome a and cytochrome oxidase. It appears to be widely accepted that these components possess the same or closely related prosthetic groups, and Lemberg (1953) has produced good evidence that haemin a is in fact the prosthetic group common to both moieties. In general, the two-banded type of spectrum is found when the metal bonds are covalent, e.g. in oxyhaemoglobin. The ionic complexes, such as reduced haemoglobin, usually show a more diffuse absorption spectrum. Reduced cytochrome a has a visible absorption band at a wavelength (605 m,.) longer than that of copper-porphyrin a and pyridine-haemochrome a (598 and 587 mz. respectively). The absence of a strong ,-band is common to all three pigments, and is attributable to the presence of a free aldehyde group, as conversion into the oxime results in a stronger ,-band. The apoprotein of the cytochrome must be responsible for the significant difference between the position of the absorption bands of cytochrome a and pyridinehaemochrome a. SUMMARY